Kindle Unlimited is a platform where a copious amount of audiobooks and ebooks are available for people who pay a small monthly fee. Amazon normally gives away a free 30 day trial to test out the platform, but Groupon is currently giving away a 60 day free trial.
One of the problems with Kindle Unlimited is that you will not find many best sellers, since major publishers are not onboard with giving their content away for free. The vast majority of content are from indie authors, mixed in with a few big franchises such as Hunger Games and Harry Potter.

Michael Kozlowski is the Editor in Chief of Good e-Reader. He has been writing about audiobooks and e-readers for the past ten years. His articles have been picked up by major and local news sources and websites such as the CBC, CNET, Engadget, Huffington Post and the New York Times.